Technical Tutorials

Metrics tell you a service is slow. Traces tell you which requests are slow. Profiling tells you which function is slow — the actual line of code that's consum

The first time I worked at a company that deployed continuously, I noticed something odd: code went to production multiple times a day, but users saw changes ma

The first rate limiter I wrote was a counter in Redis with a TTL. It worked, sort of, but it had a problem I didn't notice until someone pointed it out: a clien

I built a two-person video call feature last year. The expectation, from a product perspective, was "like Zoom but embedded in our app." The reality of WebRTC i

My first data pipeline was a directory of SQL files run by a cron job. daily_revenue.sql, user_cohorts.sql, and a shell script that ran them in order and droppe

I avoided WebAssembly for years because the examples always involved rendering 3D graphics or running Photoshop in a browser, which aren't problems I have.

I added a service worker to a small web app last month, mostly to see if the "install to home screen" prompt would show up. It did, and the app now opens in its

I built my first FastAPI service after five years of Flask, expecting it to be a similar experience with slightly nicer type hints. It's not. FastAPI changes wh

I once spent a day optimizing a Python data pipeline, cutting its runtime from 40 minutes to 35 by rewriting loops as comprehensions and caching function result

A user clicks "Pay now." The request reaches your server, charges the card, and then the connection drops before the response gets back. The user clicks again.

I avoided end-to-end tests for years because every setup I tried was fragile. Selenium needed a driver per browser. Cypress was pleasant until I needed multiple

I once wrote a Node script that read a 4GB log file into memory, filtered it, and wrote the result back out. On my laptop it worked. On the production box with

React Server Components have been the most confusing part of React's evolution, partly because the explanations keep mixing them up with Server-Side Rendering,

I put off adding type hints to my Python projects for years because the examples in the docs always looked like they were solving problems I didn't have. Th

Media queries have always had a fundamental problem: they tell you the size of the viewport, but components don't live in the viewport — they live in a contain

Go's concurrency is sold as simple, and it is, once you stop trying to map it onto threads. The confusion usually comes from treating goroutines like threads an

I've seen SQLite dismissed in architecture discussions so many times that I stopped bringing it up. Then I built two projects on it that handled more traffic th

Vite is known as a dev server for apps, but it's also a solid build tool for npm packages. The library mode is less documented than the app workflow, and the de

I built a small internal tool last month and started reaching for React out of habit. Then I looked at what the tool actually did: display a list, let users edi

I put off learning Rust for two years because every introduction led with "Rust has no garbage collector and enforces memory safety at compile time" and then do

Most developers learn Promises by copying patterns. .then().catch(), Promise.all, and if they're lucky, they never think about it again. That works until it doe

Everyone learns with open(...) as f on day one and then stops thinking about it. The with statement is a general mechanism for "do setup, do work, do teardown,

Time zone bugs are unusually nasty because they pass every test you write and fail twice a year in production, usually at 2am local time on a Sunday. Python's s

Node processes that grow steadily until the container gets OOM-killed are a specific kind of frustrating, because the service looks healthy right up until it do

Go's encoding/json package is one of those things that feels clunky for about a week and then feels obvious. The friction comes from the same place Go's frictio